I
Ice Czar
Guest
Corruption 101
There sometimes seems to be a few hundred ways to munge your data
my personal list of probability based on
The Risks To Your Data @ the PC Guide
(with a few additions, and split into hardware, software and filesystem)
Hardware Failure
Memory Errors: With so many systems today running without error detection or correction on their system memory, there is a chance of a memory error corrupting the data on the hard disk. It is rare for it to happen, but it does happen.
Test your RAM with memtest86+ and or memtest86 Memtest, consider a board that supports ECC RAM
Power Loss: Losing power at the wrong time, such as when you are doing sensitive work on your hard disk, can easily result in the loss of many files
Use a high quality PSU with stable voltage, employ a UPS or other line conditioning, avoid hard restarts
Cables not included on the PCGuide's original list it is none the less an importatnt possibility, especially with todays transfer speeds, there is a very real reason that the industry is adopting SATA over PATA see post below for a full discussion and links
System Timing Problems: Setting the timing for memory or cache access too aggressively, or using a hard disk interface transfer mode that is too fast for the system or device, can cause data loss. This is often not something that will generally be realized until after some amount of damage has been done.
see tRAS below, bump back an overclock, try a different divider, dont overclock if you cant lock the PCI bus, I would bump the probability of this up a few slots if the machine is overclocked, otherwise I ve put it here
Resource Conflicts: Conflicts resulting from peripherals that try to use the same interrupt requests, DMA channels or I/O addresses, can cause data to become corrupted.
Review PIRQ routing and manual assignment of IRQs in the worse case senerio, chipset specific but a good overview
The Hard DriveTest with the manufacturers Diagnostic, most of the rest is preventative, proper handling vibration free and cool environment, with clean air and stable floor
Software Failure
Busmastering Drivers
Filesytem Corruption
Power Issues
There are three basic areas of power problems
1.Source Power Brown outs, blackouts, spikes\surges ect.
see > Power Conditioning and DIY UPS @ Dans Data, for the basics
In this category I would also place power issues due to pilot error, hard restarts and shorts, avoid both. Shutdown properly and pay attention when mounting your motherboard and routing power cables.
2. Under Power: Basically too many components for the power supply,
dont be decieved by wattage figures, its the amount of amps per rail that is really important.
See > Choosing the right Power Supply &
takaman's Power Supply Calculator rev0.61x
to determine the amps you need per rail
3. Voltage Stability Pretty much the all the following
[H]ardcore PSU info (Charts)
http://terasan.okiraku-pc.net/dengen/tester/index.html
http://terasan.okiraku-pc.net/dengen/tester2/index.html
(note the PC Power & Cooling, Antec, Ablecom, and Zippy)
In Japanese
But the graphs speak volumes
and the PSU are identified in English]
http://terasan.okiraku-pc.net/dengen/tester/index.html
note the consistent voltage instability at startup and shortly thereafter in those graphs
Winbond Launches New Bus Termination Regulator April 4th 2003
"Winbond Electronics Corporation, a leading supplier of semiconductor solutions, today launched the W83310S, a new DDR SDRAM bus termination regulator. The solution, new to Winbond's ACPI product family, is aimed at desktop PC and embedded system applications with DDR SDRAM requirements.
Computer systems architectures continue to evolve and are becoming more complex; CPU and memory speeds continue to increase ever more rapidly with every technology turn. More and more high current/low voltage power sources are required for PC systems. This is particularly true for high-speed components such as CPU, memory, and system chipsets. The performance of these components is highly dependent upon stable power. Therefore, motherboard designers require accurate, stable, low-ripple and robust power solutions for these components.
Many system designs use discrete components to implement bus termination functions. This approach creates several problems including poorer quality load regulation; higher voltage-ripple, increased usage of board space and inconsistent designs when different discrete components are used."
and just to reinterate this point one more time
http://www.anandtech.com/showdoc.html?i=1774&p=8
"the majority of damaged RAM returned to memory manufacturers is destoryed by fluctuations in the voltage."
the transient response is the critical measure, unfortunately its not a metric that is commonly supplied with the PSU specs
(this seems to be slowly changing, as some manufacturers are supplying the transient response now)
Transient Response: As shown in the diagram here, a switching power supply uses a closed feedback loop to allow measurements of the output of the supply to control the way the supply is operating. This is analogous to how a thermometer and thermostat work together to control the temperature of a house. As mentioned in the description of load regulation above, the output voltage of a signal varies as the load on it varies. In particular, when the load is drastically changed--either increased or decreased a great deal, suddenly--the voltage level may shift drastically. Such a sudden change is called a transient. If one of the voltages is under heavy load from several demanding components and suddenly all but one stops drawing current, the voltage to the remaining current may temporarily surge. This is called a voltage overshoot.
Transient response measures how quickly and effectively the power supply can adjust to these sudden changes. Here's an actual transient response specification that we can work together to decode: "+5V,+12V outputs return to within 5% in less than 1ms for 20% load change." What this means is the following: "for either the +5 V or +12 V outputs, if the output is at a certain level (call it V1) and the current load on that signal either increases or decreases by up to 20%, the voltage on that output will return to a value within 5% of V1 within 1 millisecond". Obviously, faster responses closer to the original voltage are best."
There sometimes seems to be a few hundred ways to munge your data
my personal list of probability based on
The Risks To Your Data @ the PC Guide
(with a few additions, and split into hardware, software and filesystem)
Hardware Failure
Memory Errors: With so many systems today running without error detection or correction on their system memory, there is a chance of a memory error corrupting the data on the hard disk. It is rare for it to happen, but it does happen.
Test your RAM with memtest86+ and or memtest86 Memtest, consider a board that supports ECC RAM
Power Loss: Losing power at the wrong time, such as when you are doing sensitive work on your hard disk, can easily result in the loss of many files
Use a high quality PSU with stable voltage, employ a UPS or other line conditioning, avoid hard restarts
Cables not included on the PCGuide's original list it is none the less an importatnt possibility, especially with todays transfer speeds, there is a very real reason that the industry is adopting SATA over PATA see post below for a full discussion and links
System Timing Problems: Setting the timing for memory or cache access too aggressively, or using a hard disk interface transfer mode that is too fast for the system or device, can cause data loss. This is often not something that will generally be realized until after some amount of damage has been done.
see tRAS below, bump back an overclock, try a different divider, dont overclock if you cant lock the PCI bus, I would bump the probability of this up a few slots if the machine is overclocked, otherwise I ve put it here
Resource Conflicts: Conflicts resulting from peripherals that try to use the same interrupt requests, DMA channels or I/O addresses, can cause data to become corrupted.
Review PIRQ routing and manual assignment of IRQs in the worse case senerio, chipset specific but a good overview
The Hard DriveTest with the manufacturers Diagnostic, most of the rest is preventative, proper handling vibration free and cool environment, with clean air and stable floor
Software Failure
Busmastering Drivers
Filesytem Corruption
Power Issues
There are three basic areas of power problems
1.Source Power Brown outs, blackouts, spikes\surges ect.
see > Power Conditioning and DIY UPS @ Dans Data, for the basics
In this category I would also place power issues due to pilot error, hard restarts and shorts, avoid both. Shutdown properly and pay attention when mounting your motherboard and routing power cables.
2. Under Power: Basically too many components for the power supply,
dont be decieved by wattage figures, its the amount of amps per rail that is really important.
See > Choosing the right Power Supply &
takaman's Power Supply Calculator rev0.61x
to determine the amps you need per rail
3. Voltage Stability Pretty much the all the following
[H]ardcore PSU info (Charts)
http://terasan.okiraku-pc.net/dengen/tester/index.html
http://terasan.okiraku-pc.net/dengen/tester2/index.html
(note the PC Power & Cooling, Antec, Ablecom, and Zippy)
In Japanese
But the graphs speak volumes
and the PSU are identified in English]
Continuous Power vs. Peak Power at Spin-Up
12V power profile (current vs. time) of an IDE/ATA hard disk at startup. You can see that the peak power draw is over quadruple
the steady-state operating requirement. The graph appears "noisy"
due to frequent oscillations in current requirements
refering to the links above againPeak vs. Continuous Power
Despite this extra capacity, it is still a good idea to not load up your system to the very limit of your power supply's stated power capacity. It is also wise, if possible to employ features that delay the startup of some disk drive motors when the PC is first turned on, so the +12 voltage is not overloaded by everything drawing maximum current at the same time.
http://terasan.okiraku-pc.net/dengen/tester/index.html
note the consistent voltage instability at startup and shortly thereafter in those graphs
Winbond Launches New Bus Termination Regulator April 4th 2003
"Winbond Electronics Corporation, a leading supplier of semiconductor solutions, today launched the W83310S, a new DDR SDRAM bus termination regulator. The solution, new to Winbond's ACPI product family, is aimed at desktop PC and embedded system applications with DDR SDRAM requirements.
Computer systems architectures continue to evolve and are becoming more complex; CPU and memory speeds continue to increase ever more rapidly with every technology turn. More and more high current/low voltage power sources are required for PC systems. This is particularly true for high-speed components such as CPU, memory, and system chipsets. The performance of these components is highly dependent upon stable power. Therefore, motherboard designers require accurate, stable, low-ripple and robust power solutions for these components.
Many system designs use discrete components to implement bus termination functions. This approach creates several problems including poorer quality load regulation; higher voltage-ripple, increased usage of board space and inconsistent designs when different discrete components are used."
and just to reinterate this point one more time
http://www.anandtech.com/showdoc.html?i=1774&p=8
"the majority of damaged RAM returned to memory manufacturers is destoryed by fluctuations in the voltage."
the transient response is the critical measure, unfortunately its not a metric that is commonly supplied with the PSU specs
(this seems to be slowly changing, as some manufacturers are supplying the transient response now)
Transient Response: As shown in the diagram here, a switching power supply uses a closed feedback loop to allow measurements of the output of the supply to control the way the supply is operating. This is analogous to how a thermometer and thermostat work together to control the temperature of a house. As mentioned in the description of load regulation above, the output voltage of a signal varies as the load on it varies. In particular, when the load is drastically changed--either increased or decreased a great deal, suddenly--the voltage level may shift drastically. Such a sudden change is called a transient. If one of the voltages is under heavy load from several demanding components and suddenly all but one stops drawing current, the voltage to the remaining current may temporarily surge. This is called a voltage overshoot.
Transient response measures how quickly and effectively the power supply can adjust to these sudden changes. Here's an actual transient response specification that we can work together to decode: "+5V,+12V outputs return to within 5% in less than 1ms for 20% load change." What this means is the following: "for either the +5 V or +12 V outputs, if the output is at a certain level (call it V1) and the current load on that signal either increases or decreases by up to 20%, the voltage on that output will return to a value within 5% of V1 within 1 millisecond". Obviously, faster responses closer to the original voltage are best."